Hello chonchos,
welcome to the Polycom Community.
What type of SIP Server are you using and are you sure the Polycom phones are producing this "tone" and it is not some kind of server generated tone played into the line?
We would need some more details and probably logs. Please provide some kind of update.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Best Regards
Steffen Baier
Polycom Global Services
